Such air-drying systems are known in the state of the art, and are, for example, distributed by the company Knorr-Bremse. FIG. 2 shows such a prior art-drying system. According to FIG. 2, a cold generating adsorption dryer in a two-chambered embodiment is operated in a two-phase manner, i.e. one drying phase and one regeneration phase are carried out in parallel or simultaneously with one another. While the main airstream is dried in one chamber, for example the right chamber 1R, chamber ) the drying agent in the other chamber 1L is regenerated. As the air flows through the drying agent or adsorbate 37R in the right chamber 1R, the water contained in the air is extracted therefrom to such an extent that the relative humidity of the main airstream upon exiting the right chamber is less than or equal to 35%.
A portion of the dried air is branched off from the main air-stream, expanded through a regeneration line 41 with a regeneration nozzle or orifice 47, arranged therein and blown through the saturated drying agent 37L of the second chamber 1L before being finally exhausted into the atmosphere. The moisture that has been adsorbed into the drying agent 37L in the left chamber 1L during the prior drying phase is now extracted from the drying agent 37L by the extremely dry air passing therethrough. From time to time the functional operating cycle is switched between the two chambers as needed.
In pneumatic systems of rail vehicles, two compressors are often used for long trains and high air consumption in order to reduce the system filling time. In such a case when two compressors are employed for filling, one of the compressors is switched off upon reaching a predetermined system pressure. The normal functional operation is then taken over and carried out by one compressor alone. For cost reasons, the air-stream of both compressors is directed through a single air dryer. In order to prevent an over-saturation of the air-drying system, the regeneration orifice is therefore designed and dimensioned for providing a proper regeneration airflow for the operation of two compressors. In other words basically the regeneration orifice is over-dimensioned for normal operation with one compressor. This results in an excessive air and energy consumption during normal operation.